Performance of load-bearing precast concrete wall with base isolation subjected to seismic loadings

Abstract

The government of Malaysia has been strongly encouraging local construction industry to utilize Industrialized Building System (IBS) to reduce dependence on foreign workers and improve site safety and construction duration. This study investigated the seismic performance of a locally developed precast concrete wall system by local system supplier, namely the HC Precast System (HCPS). The system used load-bearing precast infill panel which was connected to adjacent columns through shear keys and dowel bars protruded by both sides of the wall panel. This type of precast system is not currently covered by Eurocode 8. A full-scale single bay, double storey prototype structure consisted of HCPS was constructed and tested under lateral quasi-static loading at laboratory of Construction Research Institute of Malaysia (CREAM). Displacement-controlled cyclic loading of 0.05%, 0.20%, 0.40%, 0.50% and 0.70% roof drift was applied to the prototype structure to obtain the force-displacement hysteresis loops. Observation from the quasi-static test revealed concentration of damage along the wall-to-column interface. Thus, a finite element modeling method was proposed to represent the nonlinearity of the interface element in the numerical model. Next, a 1:3 scaled down of the prototype HCPS was designed and constructed for shake table test. Besides scaling of the test specimen, characteristics of 8 selected ground motions were also scaled correspondingly according to similitude law including the time steps and peak acceleration values. The proposed FEM model was found to be in good agreement with both quasi-static and shake table tests. The verified FEM model was used to generate capacity curves of HCPS by pushover analysis with four different lateral loading configurations respectively. The characteristic of the capacity curves and obtained behaviour factor was compared to the Equal Displacement Rule (EDR) method recommended by Eurocode 8. Thus N2Disp, a method for engineers to estimate the nonlinear displacement of HCPS from linear analysis was proposed. Seismic response of HCPS under Malaysia earthquake loading was carried out with Modal Response Spectrum Analysis (MRSA) and pushover analysis with design ground acceleration ag values of 0.05g, 0.075g and 0.1g. It was found that in all three ag levels, the performance of HCPS remained within Immediate Occupancy (I0) level. High damping rubber bearing (HDRB) was designed to provide seismic base isolation of HCPS at target period of 2.5s. The HDRB was designed, manufactured and tested at real size to obtain the dynamic property such as compressive and lateral stiffness as well as hysteresis damping ratio. The nonlinear base isolated model of HCPS was analyzed for 33 time histories representing a wide variety of epicenter distance, magnitude, soil classification and acceleration to velocity (a/v) ratio. It was revealed that while base isolation provided effective reduction in floor acceleration responses (up to 97%) in most time history cases, adverse results (amplification) were observed in ground acceleration having low (a/v) ratio and providing higher damping ratio (i.e. B = 24%) at the isolation system.